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Post by Phil Sutton on Apr 24, 2009 15:13:11 GMT
I know that the best place to feed water into a boiler is some where along the barrel,but is there any reason not to feed in via the backhead,as in Talyllyn?
TIA
Phil
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redmog
Part of the e-furniture
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Posts: 461
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Post by redmog on Apr 24, 2009 16:01:40 GMT
I know that the best place to feed water into a boiler is some where along the barrel,but is there any reason not to feed in via the backhead,as in Talyllyn? TIA Phil A good question. I shall take interest in the responses to this one because I don't know the answer! Is there a previous thread on this ? My B1's injectors feed via the backhead without any problems. Chris
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Post by baggo on Apr 24, 2009 16:23:09 GMT
Hi Phil,
I imagine the main reason for feeding into the backhead is probably convenience, certainly in models. It's not the best situation as you are feeding relatively cold water into the hottest part of the boiler causing rapid cooling of the boiler and possible thermal shock. I believe full size boilers with the clacks on the backhead had internal pipes to carry the water forwards (as Paul has done on his 7F). Don Young did this on his boilers with backhead feeds.
Often it's the case that you have 3 or more feeds into a boiler (axle pump, hand pump, and 2 injectors) so it's difficult to find room for all the clacks unless you use one clack for 2 feeds. I feed the pumps into the clacks at the front of the boilers and the injectors into the backhead. At least the water from the injectors is about 60°C so does not cause so much cooling as the cold water from the pumps.
Apparently, Sir Nigel Gresley would not entertain top feeds on his locos and removed them from locos so fitted.
John
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Post by Phil Sutton on Apr 24, 2009 18:38:55 GMT
The reason I ask is that the 1400 I am putting together has a top feed,and I wanted to have a model of one that didn't,so I was going to plumb the axle pump feed through to one of the backhead clacks(injector and hand pump),blocking off the top feed bush.I don't know if it would be possable to fix a pipe to a backhead clack and feed the water further forward.All ideas welcome!
Phil
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Post by peterseager on Apr 24, 2009 19:40:40 GMT
My Simplex has no problems with the clacks on the backhead as per the drawing. But these are both fed by injectors. The hand pump has a clack halfway up the front of the boiler. This used to be fed by the axle pump until it was removed and once the rubber ball jammed so the clack remained open whereupon the boiler proceeded to drain itself through the bye-pass valve. It was early days and I did not think to shut the valve but dropped the fire smartish.
Leaving the Simplex boiler full after a run is also a problem because some water runs back and out of the injectors, especially when transported in the car.
This has led me to believe top feeds are best because the boiler would not drain in these situations. Unfortunately we are usually committed by the prototype being modeled.
Peter
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